Various electronic devices are loaded into a moving object such as an automobile, in which a wire harness is wired to supply electric power from a power supply such as a battery to these electronic devices or transmit control signals from a control unit. The wire harness includes a plurality of electric wires and terminal fittings which are attached to terminals of the electric wires.
Each of such kind of electric wires includes a core wire which is formed by twisting a plurality of conductive strands, and an insulative coating which coats the core wire. The core wire, which is exposed by removing the coating at a terminal of the electric wire, is welded to the terminal fitting. The core wire and the terminal fitting are ultrasonically welded.
As shown in FIG. 6, a terminal fitting 50 includes a welded part 55, to which an exposed core wire 53 is welded, and a mounting part 59 which is provided with a circular through hole 57 through which an electronic device or the like is electrically connected. When ultrasonic welding is performed, the exposed core wire 53 is placed between a pair of side walls 61 which the welded part 55 of the terminal fitting 50 is provided with, and a horn 63 is inserted between the pair of side walls 61 from above the exposed core wire 53. By applying ultrasonic vibration to the core wire 53 while the horn 63 is pressed against the core wire 53, the core wire 53 is ultrasonically welded to the welded part 55 (for example, refer to PTL 1.).